Kenkyu War

The Kenkyu War (named for the Kenkyu Era of April 1190-April 1199) was a war in Japan caused by the realm divide of the Kamakura Minamoto. Fearful of the rise to prominence of the Kamakura Minamoto, Emperor Go-Toba declared Minamoto Yoritomo an enemy of the state and called upon every clan in Japan, including Minamoto vassals, to fight against Yoritomo's building empire. Some clans, such as the Ishikawa, stood loyal to the Kamakura Minamoto clan, while the majority of Yoritomo's vassals and allies betrayed him to fight for the Emperor.